Objective:To explore the effect of 1,25-dihydroxyvitamin D3 on the mast cell tryptase (MCT) in asthmatic guinea pigs. Methods:A total of 60 male or female healthy guinea pigs were randomly divided into control group (group A), asthmatic group(group B), and 1,25-dihydroxyvitamin D3 group(group C), with 20 cases in each group. To establish asthmatic guinea pig models, 1ml peanut oil was filled into stomach in the morning in group A and group B , and 1ml peanut oil with 1,25-dihydroxyvitamin D3 was filled into stomach in group C. Airway resistance (Re) of asthmatic guinea pigs was detected, and the bronchoalveolar lavage fluid (BALF) cells were counted. Lung tissue with HE and MCT immunohistochemical staining were used to observe the pathological changes in lung tissue and the distribution of MCT. Results:After injection of different concentration of acetylcholine chloride, the Re in group B and group C were increased significantly compared with group A (P<0.05);compared with group B, the Re in group C were decreased significantly (t=-5.385, -5.761, -6.184,-13.574, P<0.05);the total number of BALF cells and eosinophils were increased significantly in group B and C (t=19.618, 9.598, 10.854, 5.388, P<0.05);compared with group B, the total number of BALF cells and eosinophils in group C was decreased significantly (t=-5.555,-5.392, P<0.05);the number of tryptase positive cells in group B was increased significantly than that in group A (t=21.312, P<0.05), and in addition to the alveolar septum and submucosa, the cells were also distributed around blood vessels and outside the cells; the number of tryptase positive cells in group C was decreased significantly compared with group B, and the difference was statistically significant (t=5.043, P<0.05). Conclusions:After the asthmatic guinea pigs are treated with 1,25-dihydroxyvitamin D3, their BALF, Re, infiltration degree of inflammatory cells in the trachea and lung tissue and airway inflammatory reaction are reduced significantly. 1,25-dihydroxyvitamin D3has a certain inhibiting effect on the activation of mast cells and the release of MCT granules.